Its not too hard to turn a list of points (for example) into simple G-Code.
G1 X10.0 Y10.0 Z0.0 F750
Move to (x,y,z) with a feedrate of 750 mm/min
you can concatenate text with your point coordinates to create a list of G-Code commands.
You need to know if you will need to add a header and footer to your program and what needs to be in that.
You might need to include spindle commands i.e turning it on/off and setting speed.
You might need to add traversing sequences to lift the spindle and move to a point above the workpiece before moving to the start of the next machining operation.
The list goes on!
I use CAMBAM because its cheap and easy to use for 2D pockets, profiles, engraves and 3D contouring from STL mesh format. It also has some interesting user-created plugins.
Search for user Siemen on here and the old forum - he’s done some nice work creating patterned surfaces by generating G-Code.